1. Field of the Invention
The invention pertains to a drum-like container produced by blow-molding from a discontinuously extruded tubular preform of thermoplastic material, with a wall consisting of an inner layer, an outer layer, and at least one middle layer.
2. Description of the Related Art
A process and a device for the production of a large-capacity hollow body, such as a drum, out of plastic with a multi-layer wall are known from European Patent Publication 0,326,584. The device consists of an annular piston, acting as a co-extrusion head, which can slide axially in a housing; this piston has a flow channel bore extending approximately in the radial direction for each layer of the wall and thus for each plastic melt; each of these bores opens out into a ring-shaped distributor. The ring-shaped distributor then leads to a common flow channel, into which the individual plastic melts flow one after the other. The flow channel located approximately in the center of the annular piston gradually expands to the cross section of a ring-shaped reservoir upon which the annular piston acts.
In the case of storage or transport containers such as drums with a multi-layer wall, the outer layer of the wall, and thus also the layer of the preform which is blow-molded to form the drum-like container, is colored in a special way to provide protection against UV rays, for example, or to give a certain visual appearance. At the same time, however, it is also desirable to have the ability to determine at any timed, without any special measuring devices, how much liquid is still in the drum-like container simply by looking at it from the outside.
A device for the discontinuous production of a tubular, multi-layer, co-extruded preform of thermoplastic material, out of which a drum-like container is formed by the blow-molding process, is known from DE-GM 91-07,812, in which a connecting channel is provided between the ring-shaped channel for the plastic melt of the inner layer, which consists of clear or transparent plastic, and the ring-shaped channel for the outer layer, which consists of a colored plastic composition. As a result of this connecting channel, a so-called xe2x80x9cview stripxe2x80x9d can be produced in the outer layer, which makes it possible to see how much liquid is left in the finished container. If the wall of the container has more than two layers, however, it is impossible by means of this device to produce a preform for a drum-like container which has a view strip to allow the determination of the amount of liquid left in the container.
The invention is therefore based on the task of creating a drum-like container which has walls consisting of at least three layers and which makes it possible to determine the degree to which the container is filled at any time.
To accomplish this task, it is proposed in accordance with the invention that the wall of a drum-like container of the general type described above has a view strip of translucent plastic extending in the axial direction.
By means of the view strip, it is possible for the amount of material present in a container designed in this way to be monitored or checked regularly.